1.1 Scope of application
The PSL 641U line protection measurement and control device takes current and voltage protection as the basic configuration, and integrates various measurement and control functions, which is suitable for
66kV and below power distribution lines. The application fields cover power, water conservancy, transportation, petroleum, chemical, coal, metallurgy and other industries.
1.2 Protection function configuration
a) Three section compound voltage directional blocking overcurrent
b) Two segment directional zero sequence protection and zero sequence alarm
c) Overcurrent acceleration protection and zero sequence acceleration protection
d) Low cycle load shedding function
e) Low voltage load shedding function
f) Overload protection (alarm or tripping optional)
g) Three phase reclosing function
h) Small current grounding line selection function
i) PT disconnection judgment
1.3 Measurement and control function configuration
a) Current, voltage, power, power factor and other measurements
b) 14 channels of external switching value input remote signal acquisition (preferably 22 channels are optional)
c) Circuit breaker position, manual opening and accident remote signaling
d) Remote opening and closing of normal circuit breaker
e) GPS time synchronization input
2 Protection function and principle
2.1 Phase to phase overcurrent protection
When the device executes the three section overcurrent discrimination, the discrimination logic of each section is consistent, and the action conditions are as follows:
1） I? ＞ Idn; Idn is the current setting of section n, and I? Is the phase current;
2） T ＞ Tdn ； Tdn is the n-segment delay setting.
2.1.1 Interphase directional element
Adopt 90 ° wiring mode and start according to phase. With the current flowing out of the bus as the positive direction, the action range Arg (U/I) ＝ - 90 °～ ＋ 30 °, error
Difference ＜± 3 °.
2.1.2 Low voltage locking element
The low-voltage element acts when any of the three line voltages is lower than the low-voltage fixed value, and opens the locked protection element. With this element,
It can ensure that the device will not malfunction under non fault conditions such as motor feedback.
2.1.3 Negative sequence overvoltage locking element
When the negative sequence voltage is greater than the fixed value, the locked protection element will be opened. This element, together with the low-voltage locking element, forms a composite voltage locking element,
It forms compound voltage overcurrent protection with overcurrent components.
31 PSL 641U Line Protection Measurement and Control Device Instruction
thirty-two
2.2 Phase to phase current inverse time element
The inverse time protection element is a protection element whose action time limit naturally matches with the current in the protected line. By translating the action curve
It is very convenient to realize the cooperation of the whole line. The device provides three common inverse time characteristics, namely standard inverse time, very inverse time and extreme inverse time.
The inverse time characteristic is set by the "inverse time index" in the fixed value. The formula of each inverse time characteristic is as follows:
a) General inverse time limit
b) Very inverse time limit
c) Extreme inverse time limit
Where tp is the time coefficient, ranging from 0.05 to 1; Ip is the current reference value; I is fault current; T is the tripping time.
The inverse time limit of the setting value is the product of the numerator in the above expression, in seconds, and the setting range is (0.005~127).
It can also be realized for long time inverse time limit. The expression of long time inverse time limit is as follows:
For the interphase current protection of the device, the definite time limit or inverse time limit can be selected by setting the relevant bits of the control word. When the inverse time limit mode is selected,
Automatically exit the fixed time limit section III overcurrent protection, and the function platens of the interphase current section III become the interphase current inverse time limit function enable/disable platens respectively.
2.3 Zero sequence overcurrent
When the zero sequence current is used as tripping or alarm, the zero sequence current can be selected from the outside by KG1.7 bit of control word 1 in the operation parameter
The special zero sequence CT is introduced or generated by the software itself, and the device defaults to the external connection of zero sequence current.
The outlet of zero sequence overcurrent protection trips when the following conditions are met:
1) 3I0>I0n, I0n is the fixed value of grounding section n;
2) T>T0n, T0n is the fixed value of grounding n-section delay;
3) The corresponding direction conditions are met (if necessary).
2.3.1 Zero sequence directional element
The zero sequence current is in the positive direction of the bus flow to the line, and the zero sequence CT polarity terminal is connected to the 3I0 polarity terminal of the device. Connect as per the primary system neutral point low resistance
In local consideration, the action area of zero sequence directional element is set as Arg (3U0/3I0)=- 195 °~- 75 °. 3U0 is self-produced.
When the neutral point of the primary system is grounded with medium resistance or high resistance, the action area can be adjusted according to the different conditions of the system. book
Special instructions shall be given at the time of shipment.
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eighty
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one hundred and twenty
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zero point one four
zero point zero two
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=
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thirteen point five
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T tpPSL 641U Line Protection Measurement and Control Device Instruction
2.3.2 Zero sequence inverse time element
The principle of zero sequence inverse time element is the same phase overcurrent inverse time element, and the inverse time characteristic is set by the inverse time index in the setting value.
The zero sequence overcurrent protection of the device can select the definite time limit or inverse time limit mode by setting the relevant control word. When inverse time limit mode is selected, automatic
Exit the zero sequence overcurrent component of section II, and the functional pressing plate of zero sequence overcurrent section II will be changed into the enabling/disenabling pressing plate of zero sequence overcurrent inverse time limit function.
2.3.3 Zero sequence current alarm element
The zero sequence current will send an alarm signal after meeting the setting value of "zero sequence overcurrent alarm" and setting value of delay time.
2.4 Closing acceleration
It includes manual acceleration and protection acceleration. The acceleration function can be enabled or disabled through the soft pressing plate.
The starting conditions of the manual acceleration circuit are:
1) The time of the circuit breaker in the opening position exceeds 30s;
2) The circuit breaker changes from opening to closing, and the acceleration function is opened for 3s.
Manual acceleration requires input of acceleration strap, setting of acceleration current and time settings, and the acceleration mode can be realized by selecting the post acceleration mode from the control word
This function is now available. The manual acceleration protection function is put into operation separately, which can be used for charging protection of sectionalized or bus tie circuit breaker.
The protection acceleration is divided into front acceleration or post reclosing acceleration, and one of them can be selected by the control word.
The protection is set with separate overcurrent and zero current acceleration section current settings and corresponding time settings, which makes the protection configuration more
Flexibility. The overcurrent acceleration section of this protection can also select low-voltage locking and negative sequence voltage locking, but direction locking is not considered for all acceleration sections.
2.5 Three phase reclosing
It has three-phase primary reclosing and secondary reclosing functions. Enable/disenable the function by the corresponding soft strap, and enable II when the control word KG2.11=1
Secondary reclosing function.
2.5.1 Charging conditions
When the circuit breaker is closed, KKJ=1 and there is no locking reclosing signal, reclosing charging is completed after 15s. Reclosing soft strap light is on during charging
Flash, flat light after charging, no longer blinking.
2.5.2 Startup mode
After reclosing charging is completed, reclosing can be started by two ways: protection startup and non corresponding startup.
The protection startup reclosing is a protection action. After judging the breaker position and no current, open the reclosing for 10s.
In the non corresponding start reclosing mode, only TWJ contacts are used to monitor the position of the circuit breaker.
2.5.3 Reclosing mode
The reclosing mode can be selected by the control word KG2.9 to enable or disable the reclosing to check that the bus is free of voltage, and the default mode is no check.
2.5.4 Locking conditions
The reclosing will be blocked if any of the following conditions are met:
a) After the control circuit is disconnected, the locking is delayed for 10s;
b) The spring does not have high potential of energy storage terminal, and the locking is delayed for 2s;
c) Lock the high potential of the reclosing terminal, and lock it immediately;
d) When the circuit breaker is in the post opening position, reclosing and discharging;
e) Reclosing and discharging after 30s when the circuit breaker is in tripping position.
33 PSL 641U Line Protection Measurement and Control Device Instruction
2.5.5 Secondary reclosing
After the protection action, if the cause of the fault still exists, the circuit breaker will trip again if the better reclosing is unsuccessful. Allow
For a long time delay, the secondary reclosure shall be conducted after the insulation at the fault is recovered.
2.6 Under frequency load shedding
A slip blocking element is set in the logic of low-frequency load shedding function to distinguish fault conditions, motor feedback and real active power shortage.
Considering that the low-frequency load shedding function only works in the steady state, the AB phase to phase voltage is taken for calculation, and the three-phase balance voltage is still required during the test.
When this voltage (Uab) is lower than the calculated voltage of locking frequency, the low-frequency load shedding function will exit automatically.
To sum up, the criteria for the low-frequency load shedding function are:
1) Three phase balanced voltage, and Uab ＞ VBF;
2) df/dt＜F/T；
3) f＜F；
4) T＞TDZ；
5) The load current is greater than the setting value of "low-frequency protection locking current", which can be enabled or disabled through the control word KG3.2.
Set the control word KG1.12=1 to realize the low-frequency splitting function. At this time, criterion 2) is changed to df/dt>F/T. Other criteria are the same as low frequency
Criteria for load shedding elements.
If the site test conditions are not available, the function test can be omitted. If the analog quantity is correct, the accuracy is guaranteed by the software.
2.7 Low voltage load shedding
The criteria for low-voltage load shedding are:
1) Balance voltage, when the voltage drops to three lines, the voltage is less than VDY (low-voltage protection voltage setting);
2) Any line voltage is greater than 30V;
3) The voltage change per second is less than the fixed value "locking voltage change rate". If it is less than the fixed value, the state of this criterion will remain until
Reset after the pressure recovers to above the fixed value VDY;
4) T＞TDY；
5) Load current ＞ 0.1IN.
When testing this function, the applied balance voltage should change from large to small.
2.8 Overload
Overload monitoring three-phase phase current, action conditions are:
1) MAX(IΦ)＞Ifh；
2) The time is delayed to.
Wherein, Ifh is the fixed value of overload current. Overload alarm or tripping is determined by control word KG2.13.
2.9 Small current grounding line selection
When the device is used in ungrounded or low current grounding systems, and the zero sequence current of grounding fault is very small, the grounding line selection function can be used to complete
Isolate the fault. In this case, the zero sequence current must be introduced by the external dedicated zero sequence CT. When the circuit breaker is in the closing position and 3U0 is greater than 18V,
After 15s, the device generates 3U0 out of limit alarm. 3U0 out of limit alarm function is enabled when KG2.10 ＝ 1.,
The function of small current grounding line selection is jointly completed by the device and the master station. When the system has single-phase grounding fault, the master station receives any 3U0
After limit exceeding alarm, call 3U0 and 3I0 samples recorded in each device, and give grounding strategy after calculation. 3U0 out of limit alarm function in KG2.10
=1, when the circuit breaker is closed and 3U0 is greater than 18V, the device will generate 3U0 out of limit alarm after 15s.
